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Jomile
Joined: 06 Nov 2007
Posts: 5
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| Receiving RS-232 Data From HyperTerminal (16F877A) |
 Posted: Tue Nov 06, 2007 4:56 pm |
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Hello,
I have an 16F877A and MAX233 chip that i am using to communicate with a computer (hyperterminal).
I have no problem sending data to the computer using printf.
The problem I have is when trying to read data back from the computer. For example, in the code below, regardless of what character i get it is not displayed. The output in HT is "nextnextnext" as if there were no character stored in answer.
| Code: |
while(TRUE){
answer=getc();
putc(answer);
printf("next");
} |
Ultimately I want to use the "gets" command so that I can send strings but that did not work so I went to the characters. Is there something wrong with my code? (see below). I have a 20Mhz crystal. 16F877, v. 4.057
Thanks
main.c
| Code: |
#include "C:\Program Files\PICC\Projects\11-6-07\main.h"
#include <string.h>
void main()
{
char answer;
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
// TODO: USER CODE!!
printf("Welcome");
while(TRUE){
answer=getc();
putc(answer);
printf("next");
}
} |
MAIN.H
| Code: |
#include <16F877A.h>
#device adc=8
#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz)
#FUSES NOPUT //No Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCPD //No EE protection
#FUSES WRT_50% //Lower half of Program Memory is Write Protected
#use delay(clock=20000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8) |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Nov 06, 2007 5:29 pm |
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Try a very simple test program:
| Code: | #include <16F877A.h>
#fuses HS,NOWDT,NOPROTECT,BROWNOUT,PUT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
//============================
void main()
{
char c;
while(1)
{
c = getc();
putc(c);
}
}
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Jomile
Joined: 06 Nov 2007
Posts: 5
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| Posted: Wed Nov 07, 2007 12:09 pm |
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Thanks for the code.
I implemented it and still had the same problem. It turned out that the development board that I am using had a resistor between the max chip and the port. I shorted it out and now its fine.
FOLLOW UP:
When I use your test code and the printf function i can send data the hyperterminal. But when I use the PIC Wizard to make a new project my text gets cut off. For example, if i call printf("start") I get "Sta" in HT. I do not have a wdt enabled. See code below.
MAIN.C
| Code: | #include "C:\Program Files\PICC\Projects\11-7-07\main.h"
#include <string.h>
void main()
{
setup_adc_ports(AN0_AN1_AN3);
setup_adc(ADC_CLOCK_INTERNAL);
setup_psp(PSP_DISABLED);
setup_spi(SPI_MASTER|SPI_H_TO_L|SPI_CLK_DIV_4);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
// TODO: USER CODE!!
printf("Start");
}
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MAIN.H
| Code: |
#include <16F877A.h>
#device adc=8
#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz)
#FUSES NOPUT //No Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCPD //No EE protection
#FUSES WRT_50% //Lower half of Program Memory is Write Protected
#use delay(clock=20000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8) |
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frequentguest
Guest
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| Posted: Wed Nov 07, 2007 12:25 pm |
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Your PIC is going to sleep before it finishes transmitting. There is a hidden sleep instruction that is put at the end of main().
Put a while(TRUE); statement after your printf to keep this from happening.
| Code: | printf("start");
while(TRUE); |
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